534 Notices respecting New Boohs. 



agrees with that deduced theoretically by Stokes for non- 

 sinuous motion on the assumption that no slipping occurs at 

 the boundary. In such motion the resistance is proportional 

 to the velocity. 



(2) When the velocity is greater than a definite critical 

 value, the terminal velocity of small bubbles and solid spheres 

 is proportional to the radius less a small constant; it may be 

 expressed by the formula 



v _ ifP ~ (T -fl s ^ a — ha 

 \ p J vi 



where k = ^ and 7t=§ approximately. 



This would indicate a resistance varying as the velocity 

 raised to the power of three halves. 



(3) For velocities considerably greater than those just 

 considered the law of resistance is that which Sir I. Newton 

 deduced from his experiments, namely, that the resistance is 

 proportional to the square of the velocity. The resistance is, 

 in fact, given by the expression 



R = kpa 2 Y 2 . 



In discussing the resistance during the accelerated part of 

 the motion, we found indications of a somewhat sudden change 

 in the law of resistance to steady motion. This change may 

 correspond to the passage from stage 2 to stage 3 above. 



In conclusion I beg to express my thanks to Professor J. 

 J. Thomson for placing the resources of the Cavendish Labo- 

 ratory at my disposal, and for his suggestions and advice in 

 the course of the work. 



Trinity College, Cambridge. 



LI. Notices respecting Neiv Books. 



Grunchiss der AUgemeinen Chemie. Von W. Ostwald. Leipzig : 



Wilhelm Engelmann, 1899. Pp. xvi + 549. 

 rPHE appearance of a new and revised edition of this standard 

 -*- text-book will be welcomed by all students interested in the 

 subject. It is a masterly exposition by one who has himself con- 

 tributed in no small measure to the development of this compara- 

 tively recent branch of science. 



The book is divided into two parts. Part I. is subdivided into 

 six sections, each section consisting of several chapters. Section 1 

 deals with the fundamental laws of physical chemistry, the elements 

 and their laws of combination, and the periodic law. Section 2 is 

 devoted to the laws of gases and the kinetic theory. In section 3 

 are considered the general properties of liquids, the phenomena of 

 evaporation and condensation, the thermodynamics of liquids, their 

 behaviour with respect to light, and the phenomena of surface- 

 tension and viscosity. Section 4 deals with solids, crystallization, 



